The Redbreast (as I expect all/major portion of Jo Nesbo's books) uses Norway as the main backdrop. It deals with Nazi occupation and the fight between Germany and Russia, and both its allies.

From that macro perspective, The Redbreast focused into the lives of a few soldiers on the Eastern Front that were also trained at Sennheim. Their lives mingled far more than just comrades in battle. Some fought for the same love, and others admired another with a loyalty far surpassing that of a friend. These, together with the tragic events of war normally affecting soldiers in WWII, shaped the soldiers' lives consequently.

Harry Hole, from making a mistake of shooting a Secret Service employee while The President's motorcade was weaving through the country, saw himself promoted and thus, tranferred to a bigger office than before. He was tasked with menial jobs until he stumbled on a report of a Marklin rifle illegal use. He enlisted his former partner, Ellen to help figure out seemingly isolated events that he thinks might have something to do with each other. Events snowballed, bringing the lives of the past soldiers and Harry entwined together, forcing him to use his investigative powers which he had denied he has before.